Axial-flow compressor



1967 w. s. CASTLE ETAL 3,338,508

AXIAL-FLOW COMPRESSOR Filed Aug. 23, 1965 2 Sheets-Sheet 1 I N VEN TORS1957 w. s. CASTLE ETAL 3,338,508

AXIAL'FLIOW COMPRESSOR Filed Aug. 23, 1965 2 Sheets-Sheet 2 UnitedStates Patent Ofiice 3,338,568 Patented Aug. 29, 1967 3,338,508AXIAL-FLOW COMPRESSOR William S. Castle, Speedway, and Henry Ming Marand Douglas K. Thompson, Indianapolis, Ind., assigiors to General MotorsCorporation, Detroit, Mich., a corporation of Delaware Filed Aug. 23,1965, Ser. No. 481,842 8 Claims. (Cl. 230133) ABSTRACT OF THE DISCLOSUREThe stator structure of an axial-flow compressor includes a fullcylindrical case into which circular vane rings and stationary rotorshroud rings are inserted in alternating relation. The rotor shrouds fitthe interior of the case and the vane rings are spigotted onto the rotorshrounds. A set of pull rods provides for removal of this structure fromthe case. The vanes are cantilevered from the vane rings and arereinforced by a wire welded to the ring between the vanes and to theouter ends of the vanes which project through the ring.

Our invention is directed to improvements in the stationary structure ofaxial-flow compressors. The principal purpose of our invention is toprovide lightweight structures of rather large size particularly adaptedfor such uses as the compressors of lift jet engines. A compressoraccording to our invention preferably embodies a lightweight case andlightweight stator vane stages piloted in the case with vanescantilevered from the outer shroud ring. Special provisions are made forreinforcing the attachment of the vanes to the shroud ring withoutadding any significant weight and for installing and removing the statorvane stages and rotor shrouds from a circumferentially unbrokencompressor case.

The nature of the invention and the advantages thereof will be clear tothose skilled in the art from the succeeding detailed description of thepreferred embodiment of the invention and the accompanying drawingsthereof.

FIGURE 1 is a side view, with parts cut away, of a lift jet engine.

FIGURE 2 is a partial sectional view of the compressor of the enginetaken on a plane containing the axis of the engine.

FIGURE 3 is a fragmentary sectional view taken on the plane indicated bythe line 3'3 in FIGURE 2.

FIGURE 4 is a fragmentary axonometric view of a stator stage.

, FIGURE 5 is a view to a larger scale of a section similar to FIGURE 2.

FIGURE 6 is a view similar to FIGURE 5 taken on a different planecontaining the axis.

FIGURE 1 illustrates the preferred environment, a lift jet enginecomprising a compressor 9 supplying compressed air to combustionapparatus and a turbine (not illustrated) within a case 10, the turbinedriving the compressor and discharging propulsive gas through an exhaustnozzle 11. The compressor includes a rotor 13 having a forward bearingwithin a fairing 14 supported by struts 15 extending across the airinlet of the compressor. The compressor rotor forms a unitary rotatingstructure with the turbine wheel which has a bearing near the exhaustend of the engine (not shown). Fuel is supplied to the combustionapparatus of the engine from a manifold 17 through branch pipes 18.Since the structure of the engine is immaterial to the compressorstructure, it will not be further described.

, Referring to FIGURES 2, 5, and 6, the compressor 9 comprises asubstantially cylindrical sheet metal case 19 which has a forward flangeto which a cylindrical air inlet frame 21 is bolted. The air inlet framemounts the struts 15 which in turn support the fairing 14. Thecornpressor rotor 13 includes a number of lightweight disks 22 whichbear rings of rotor blades 23 pinned to them. Seal rings 24 are disposedbetween the disks. The successive stages of stator vanes 25 are mountedbetween the stages of rotor blades. These vanes extend radially inwardfrom the case 19 which is bounded by the inlet frame 21 and, so far asthe compressor rotor is concerned, at the rear end by an inwardlydirected flange 26. The stator vanes 25 are cantilevered from statorvane outer shroud rings 27 which are spaced apart axially by stationaryshroud rings 29 for the rotor stages. The rings of each of these ets areof shallow channel section, as appears most clearly in FIGURES 5 and 6.

The rings 27 and 29 are supported and centered in the case 19 by flangesdefined by rings 31 brazed to the interior of the light sheet metal case19. These rings 31 have cylindrical internal surfaces which provide apilot for the rear flange 33 of each rotor shroud ring 29 except thefinal shroud ring, which is identified as 34. The rear flange of ring 34bears against the abutment 26 of the case. The channel section statorvane shrouds 27 are disposed between and in contact with the adjacentrotor shroud rings and are supported through a number of pin and slotconnections from these rings. The rings 27 thus do not directly engagethe outer case but are held centered within the case by their connectionto the adjacent rotor shrouds. This connection is provided by a numberof headed pins 35 welded to and extending from the flange 33 into slots37 in the outwardly extending flanges at the edges of the shroud ring27. The stator vane ring 27 immediately forward of the last rotor stageis thus supported at its forward edge by the adjacent shroud ring 29 andin turn supports from its rear edge, by the same sort of connection, thefinal rotor shroud ring 34. The flanges on the shroud ring 27 are spacedfrom the pilot rings 31 and this, with the radially expansibleconnection afforded by the freedom of pins 35 in slots 37, allows forrelative expansion of the stator vane stages with re-- spect to therotor shrouds and accurately centers the vane stages in the case.

The first rotor stage shroud ring 29 is held in place by a shroud 39mounted within the inlet frame 21 which in turn is held in place whenthe inlet frame is bolted to the compressor case 19. When this isaccomplished all of the shrouds, which may be considered to be thelining of the compressor case, are held in a stack between the inletframe 21 and the flange 26 of the case.

To facilitate assembly of the rings 27 and 29 in th case, the pilotrings 31 are of slightly decreasing diameter from the front to the rearof the case and, as a practical example, the difference in diametersbetween successive pilot rings 31 may be about to of an inch. Of course,if a converging compressor case is used, the diameter step betweensuccessive rings could be much larger. With the case vertical, the rotorcan be lowered into the compressor case at the same time as the vanerings and rotor shrouds, and the shrouds and vane rings willautomatically align with the axi of the case. After this is done the airinlet housing is fitted to complete the assembly.

In order to facilitate removal of the shrouds from the interior of thecase, a number of pull rods 41 (preferably four) extending axially ofthe case are distributed around the circumference. These rods are guidedin notches 42 (FIGURE 3) in the pilots 31 and notches 43 in the flangesof the vane hrouds 27. An expanding ring 44 (FIGURE 2) is fitted to therear ends of these rods radially outward of the final rotor shroud ring34. The forward ends of the pull rods are threaded as indicated at 45.

3 When the inlet frame 21 has been removed, the rods 41 can be pulledslightly forward so that ring 44 abuts the forward flange of shroud 34.By applying a suitable tool to the threaded end of the pull rods, thestator structure may be pulled forwardly from the case, the rotor, ofcourse, moving with it.

The stator structure so far described may be quite light because nogreat forces tend to distort the structure and the effect of airpressure in the compressor is to even out any departures from exactcircular cross section. The shroud rings of both sets are lightweightand flexible and are piloted in or supported from the case so that theyare held truly circular by the case. There is no significant load on therotor shrouds, but the stator shroud rings 27 carry the vanes 25 whichare subjected to substantial dynamic loading from the air flowingthrough the compressor. By eliminating an inner shroud on these vanes,an element of structure having considerable weight is eliminated; but,with the cantilevered vanes, the entire resistance to loads on theblades must be taken through the outer shroud. It is one of theprincipal objects of our invention to provide a structure capable ofresisting these loads without any more weight than is absolutelynecessary and to simplify the fabrication of the stator rings.

The structure for this is most clearly shown in FIG- URES 3 and 4-, andalso in FIGURES 5 and 6. Each vane 25 is inserted through a suitableopening, shaped to conform to the vane, in the cylindrical web '50 ofthe shroud ring 27. These blades are brazed in place and projectslightly through the outer shroud; as a practical example, perhaps aquarter of an inch. A notch 51 is provided across the end of each bladeand zigzag bracing wire 52 extending around the shroud ring isspot-welded to the outer end of the blade at the notch 51 and to theouter surface of the shroud ring midway between each adjacent pair ofblades. Wire 52 preferably is in a number of segments or sections forconvenience in assembly. The sections of wire 52 between the points ofattachment to the shroud ring and of attachment to the vane brace thevane against any movement due to the aerodynamic lift on the vane. Thisarrangement contributes a great deal to the rigidity of the assembly andadds substantially no weight. It eliminates the need for thick ordoublelayered outer shrouds to provide suflicient anchorage for theblades.

It should be clear to those skilled in the art that the structuralfeatures of the compressor stator described herein are adapted topromote strength and reduce weight, as well as facilitate assembly anddisassembly of the compressor. It will be understood that some featuresof the invention may be dispensed with while others are retained inresponse to the requirements of other compress01 structures.

The detailed description of the preferred embodiment of the inventionfor the purpose of explaining the principles thereof is not to beconsidered as limiting or restricting the invention, since manymodifications may be made by the exercise of skill in the art.

We claim:

1. A lightweight multi-stage axial-flow compressor stator comprising, incombination,

a generally cylindrical case,

a plural number of flanges extending inwardly from the case providingcylindrical internal pilot surfaces successively decreasing slightly indiameter in one direction axially of the case,

a set of stator vane outer shroud rings,

a set of rotor stage stationary shroud rings,

the rings of the two sets alternating axially of the case,

the rings of one set being piloted in said pilot surfaces,

means on the rings supporting the rings of the other set on the rings ofthe said one set providing for relative radial expansion of the ringsand locating the other set axially and radially of the compressor,

a plural number of pull rods extending axially of the compressor pastthe rings and adapted to engage the ring at one end of the compressor sothat the rings may be disassembled from the case by pulling on the rods,

5 compressor stator vanes fixed on the vane shroud rings extendingthrough the rings and projecting outwardly from a portion of the outersurface of the ring, and

bracing wires each bonded to the outer end of a plural number of vanesand bonded to the said portion intermediate the vanes,

2;. A lightweight multi-stage axial-flow compressor stator comprising,in combination,

a generally cylindrical case,

a plural number of flanges extending inwardly from the case providingcylindrical internal pilot surfaces successively decreasing slightly indiameter in one direction axially of the case,

a set of stator vane outer shroud rings,

a set of rotor stage stationary shroud rings,

the rings of the two sets alternating axially of the case,

the rings of one set being piloted in said pilot surfaces,

means on the rings supporting the rings of the other set on the rings ofthe said one set providing for relative radial expansion of the ringsand locating the other set axially and radially of the compressor,

a plural number of pull rods extending axially of the compressor pastthe rings and adapted to engage the ring at one end of the compressor sothat the rings may be disassembled from the case by pulling on the rods,and

compressor stator vanes fixed on the vane shroud rings.

3. A lightweight multi-stage axial-flow compressor stator comprising, incombination,

a generally cylindrical case,

a plural number of flanges extending inwardly from the case providingcylindrical internal pilot surfaces successively decreasing slightly indiameter in one direction axially of the case,

a set of stator vane outer shroud rings,

a set of rotor stage stationary shroud rings,

the rings of the two sets alternating axially of the case,

the rings of one set being piloted in said pilot surfaces,

means on the rings supporting the rings of the other set on the rings ofthe said one set providing for relative radial expansion of the ringsand locating the other set axially and radially of the compressor,

compressor stator vanes fixed on the vane shroud rings extending throughthe rings and projecting outwardly from a portion of the outer surfaceof the ring, and

bracing wires each bonded to the outer end of a plural number of vanesand bonded to the said portion intermediate the vanes.

4. A lightweight multi-stage axial-flow compressor stator comprising, incombination,

a generally cylindrical case,

a plural number of flanges extending inwardly from the case providingcylindrical internal pilot surfaces successively decreasing slightly indiameter in one direction axially of the case,

a set of stator vane outer shroud rings,

a set of rotor stage stationary shroud rings,

the rings of the two sets alternating axially of the case,

the rings of one set being piloted in said pilot surfaces,

means on the rings supporting the rings of the other set on the rings ofthe said one set providing for relative radial expansion of the ringsand locating the other set axially and radially of the compressor, and

compressor stator vanes fixed on the vane shroud rings.

5. A turbomachine stator vane stage comprising, in

75 combination,

an outer shroud ring,

vanes fixed 0n and cantilevered inwardly from the shroud ring,

the shroud ring having holes configured to fit the vanes,

the vanes extending radially through the holes and projecting outwardlytherefrom, the vanes being bonded to the ring, and

bracing wire means extending circumferentially of the shroud ring bondedto the outer ends of said vanes at a point on each vane spaced outwardlyfrom the ring and bonded to the outer surface of the ring at pointscircumferentially between the vanes so as to provide braces between theouter ends of said vanes and the ring.

6. A turhomachine stator vane stage comprising, in

combination,

an outer shroud ring,

vanes fixed on and cantilevered inwardly from the shroud ring,

the shroud ring having holes configured to fit the vanes,

the vanes extending radially through the holes and projecting outwardlytherefrom, the vanes being bonded to the ring,

the vanes having notches in their radially outer ends spaced outwardlyfrom the ring, and

bracing wire means extending circumferentally of the shroud ring bondedto said vanes within the notches thereof and bonded to the outer surfaceof the ring at points circumferentially between the vanes so as toprovide braces between the outer ends of said vanes and the ring.

7. A turbomachine stator vane stage comprising, in

combination,

a outer shroud ring having a generally cylindrical portion and flangesprojecting radially outward at the edges of the said portion,

vanes fixed on and cantilevered inwardly from the shroud ring,

the shroud ring having holes configured to fit the vanes,

the vanes extending radially through the holes and projecting outwardlytherefrom between the flanges, the vanes being bonded to the ring, and

bracing wire means extending circumferentially of the shroud ring bondedto the outer ends of said vanes at a point on each vane spaced outwardlyfrom the ring and bonded to the outer surface of the cylindrical portionof the ring at points circumferentially between the vanes so as toprovide braces between the outer ends of said vanes and the ring.

8. A turbomachine stator vane stage comprising, in

combination,

a outer shroud ring having a generally cylindrical portion and flangesprojecting radially outward at the edges of the said portion,

vanes fixed on and cantilevered inwardly from the shroud ring,

the shroud ring having holes configured to fit the vanes,

the vanes extending radially through the holes and projecting outwardlytherefrom between the flanges, the vanes being bonded to the ring,

the vanes having notches in their radially outer ends spaced outwardlyfrom the ring, and

bracing wire means extending circumferentially of the shroud ring bondedto said vanes within the notches thereof and bonded to the outer surfaceof the cylindrical portion of the ring at points circumferentiallybetween the vanes so as to provide braces between the outer ends of saidvanes and the ring.

References Cited UNITED STATES PATENTS 764,450 7/ 1904 Geisenhoner253--77 1,720,754 7/1929 Baumann 25377 2,772,856 12/1956 Kent et a1230133 2,885,768 5/1959 Shinn 230-133 2,942,844 6/1960 Neate 25378FOREIGN PATENTS 267,405 3/ 1927 Great Britain.

622,895 5/ 1949 Great Britain.

661,178 11/1951 Great Britain.

748,912 5/1956 Great Britain.

779,056 7/ 1957 Great Britain.

DONLEY I. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner.

1. A LIGHTWEIGHT MULTI-STAGE AXIAL-FLOW COMPRESSOR STATOR COMPRISING, INCOMBINATION, A GENERALLY CYLINDRICAL CASE, A PLURAL NUMBER OF FLANGESEXTENDING INWARDLY FROM THE CASE PROVIDING CYLINDRICAL INTERNAL PILOTSURFACES SUCCESSIVELY DECREASING SLIGHTLY IN DIAMETER IN ONE DIRECTIONAXIALLY OF THE CASE, A SET OF STATOR VANE OUTER SHROUD RINGS, A SET OFROTOR STAGE STATIONARY SHROUD RINGS, THE RINGS OF THE TWO SETSALTERNATING AXIALLY OF THE CASE, THE RINGS OF ONE SET BEING PILOTED INSAID PILOT SURFACES, MEANS ON THE RINGS SUPPORTING THE RINGS OF THEOTHER SET ON THE RINGS OF THE SAID ONE SET PROVIDING FOR RELATIVE RADIALEXPANSION OF THE RINGS AND LOCATING THE OTHER SET AXIALLY AND RADIALLYOF THE COMPRESSOR, A PLURAL NUMBER OF PULL RODS EXTENDING AXIALLY OF THECOMPRESSOR PAST THE RINGS AND ADAPTED TO ENGAGE THE RING AT ONE END OFTHE COMPRESSOR SO THAT THE RINGS MAY BE DISASSEMBLED FROM THE CASE BYPULLING ON THE RODS, COMPRESSOR STATOR VANES FIXED ON THE VANE SHROUDRINGS EXTENDING THROUGH THE RINGS AND PROJECTING OUTWARDLY FROM APORTION OF THE OUTER SURFACE OF THE RING, AND BRACING WIRES EACH BONDEDTO THE OUTER END OF A PLURAL NUMBER OF VANES AND BONDED TO THE SAIDPORTION INTERMEDIATE THE VANES.